1. Field of the Invention
The invention relates generally to connecting a wire to a contact element and, more particularly, to a method for connecting at least one wire to a contact element to facilitate connection of the wire to a power source comprising the steps of preparing a contact element which is fitted with a groove for receiving the wire, whereby the groove preferably is deeper than the diameter of the wire, and whereby at least one wire is inserted into the groove of the contact element.
2. Background of the Invention
Such a connection method is described in U.S. Pat. No. 5,674,588 which describes a method by which a contact element, namely a forked contact plug, is inserted into a welding sleeve to embed a wire. To achieve good electric contact it is essential that the width of the groove formed between the forked legs is smaller than the diameter of the wire to ensure good cold connection. However, this also means that the cross-sectional area of the wire changes or becomes smaller, which restricts electricity flow through the wire.
A similar method is described in U.S. Pat. No. 5,269,713. Two manual steps are necessary to connect the wire to the contact element. Firstly, a rivet head is deformed with relatively great effort by means of mechanical cold working into the desired shape. A special version of wobble technique is used for this that rotates and/or eccentrically moves the riveting hammer head which causes both facing surfaces of the riveting head to be clinched into, among other places, the groove, which in turn captures the wire in said groove. The rotating movements achieve a sideward movement towards the wire which is advantageous to achieving good contact. However, with this method, the wire is exposed to such significant force that it could deform. The flattening associated with this method deforms and reduces the size of the relatively small contact surface area of the wire cross-sectional area. In the second step, the flat electrode is placed on the flat or slightly rounded rivet head. Naturally, it is advantageous if the shape of both the rivet head and the electrode is flat, since the flatter the rivet head is, the larger the contact surface is between the electrode and the rivet head which benefits the subsequent transfer of high flows of current. Possible positioning inaccuracies between the electrode and the contact surface can also be better compensated for. The flow of current induced by resistance welding generates heat which could cause the wire lacquering to melt and evaporate. However, since the wire is completely sealed prior to the welding process, complete softening of the lacquer steam is prevented which could cause entrapments in the border area between wire and rivet head.
U.S. Pat. No. 3,093,887 discloses a method for securing a part onto a plate. Rivets fitted with a structured cladding with, for example, a grooved surface are used. In the head of said cladding is a slit for receiving a wire.
U.S. Pat. No. 6,064,026 discloses a wire inserted into a fork-shaped receiver whereby the fork pegs subsequently are pressed together to catch the wire and to penetrate any possible insulation material. A flow of current is introduced to the fork pegs by means of a welding electrode to produce an electric connection while the wire cross-section contour is deformed. The wire is not embedded.
CH 612 489 discloses a welding sleeve made from thermoplastic material that can be used employing heating coil welding techniques.
The object of the invention is a method for connecting a wire to a contact element that ensures improved high and low current stability in the generated surface junctions to the wire.
It is a further object of the invention to provide a method for connecting a wire to a contact element that preserves the cross-sectional area of the wire but that remains fully automatic.